Apparatus for the transmission and reception of data and method for digital radio communication

BACKGROUND OF THE INVENTION

Field of the Invention

0001The present invention relates to a transmission apparatus, reception apparatus and digital radio communication method, which is used for digital radio communications.

Description of the related Art

0002As a conventional digital modulation system, a technology described in the Unexamined Japanese Patent Publication No. <patcit id="pcit0001" dnum="JPHEI1196924B"><text>HEI 1-196924</text></patcit> is known. This is the technology which the transmitting side configures a frame by inserting 1 known pilot symbol for every N data symbols and the receiving side estimates a frequency offset and amount of amplitude distortion by using the pilot symbol, and removes these frequency offset and amplitude distortion and demodulates.

0003Here, in the case of a radio communication, fluctuations in the transmission path occur due to fading and in terrestrial mobile communication in particular, fluctuations in the transmission path are not uniform. When fluctuations in the transmission path are intense, the interval of inserting a pilot symbol must be shorter to prevent deterioration of the data demodulation error rate. On the contrary, when fluctuations in the transmission path are gentle, extending the interval of inserting a pilot symbol does not deteriorate the data demodulation error rate so much.

0004On the other hand, when the level of a reception signal on the receiving side is small, a modulation system used must be highly resistant to errors for information symbols. On the contrary, when the level of a reception signal on the receiving side is large, higher priority can be given to a modulation system of high transmission efficiency for information symbols.

0005However, in the conventional digital modulation system above, the pilot symbol insertion interval and the information symbol modulation system are fixed. Therefore, when fluctuations in the transmission path are intense or the level of the reception signal of the receiver is small, error resistance during data demodulation reduces and the quality of data deteriorates. On the other hand, when fluctuations in the transmission path are gentle or the level of the reception signal on the receiving side is large, the data transmission efficiency cannot be improved despite the excessive data quality.

SUMMARY OF THE INVENTION

0006It is an object of the present invention to provide a transmission apparatus, reception apparatus and digital radio communication method capable of flexibly improving the data transmission efficiency and the quality of data.

0007The present invention attains the above object by changing the interval of inserting a known pilot symbol, binary phase (BPSK: Binary Phase Shift Keying) modulation symbols or quadrature phase (QPSK: Quadrature Phase Shift Keying) modulation symbols and the modulation system of information symbols according to the communication situation such as fluctuations in the transmission path and the level of a reception signal.

BRIEF DESCRIPTION OF THE DRAWINGS

0008The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one example is illustrated by way of example, in which; <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG.1</figref> is a block diagram showing a configuration of a transmission apparatus according to Embodiment 1 of the present invention;</li><li><figref idref="f0002">FIG.2</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of Embodiment 1 of the present invention;</li><li><figref idref="f0003">FIG.3</figref> is a layout of signal points of 16QAM and a known pilot symbol on an in-phase I - quadrature Q plane;</li><li><figref idref="f0004">FIG.4</figref> is a layout of signal points of 8PSK modulation and a known pilot symbol on an in-phase I - quadrature Q plane;</li><li><figref idref="f0005">FIG.5</figref> is a block diagram showing a configuration of a reception apparatus according to Embodiment 1 of the present invention;</li><li><figref idref="f0006">FIG.6</figref> is a block diagram showing a configuration of a transmission apparatus according to Embodiment 2 of the present invention;</li><li><figref idref="f0007">FIG.7</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of Embodiment 2 of the present invention;</li><li><figref idref="f0008">FIG.8</figref> is a layout of signal points of 16QAM and BPSK modulation on an in-phase I - quadrature Q plane;</li><li><figref idref="f0009">FIG.9</figref> is a layout of signal points of 8PSK modulation and BPSK modulation on an in-phase I - quadrature Q plane;</li><li><figref idref="f0010">FIG.10</figref> is a block diagram showing a configuration of a reception apparatus according to Embodiment 2 of the present invention;</li><li><figref idref="f0011">FIG.11</figref> is a block diagram showing a configuration of a transmission apparatus according to Embodiment 3 of the present invention;</li><li><figref idref="f0012">FIG.12</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of Embodiment 3 of the present invention;</li><li><figref idref="f0013">FIG.13</figref> is a layout of signal points of 16QAM and QPSK modulation on an in-phase I - quadrature Q plane;</li><li><figref idref="f0014">FIG.14</figref> is a layout of signal points of 8PSK modulation and QPSK modulation on an in-phase I - quadrature Q plane;</li><li><figref idref="f0015">FIG.15</figref> is a block diagram showing a configuration of a reception apparatus according to Embodiment 3 of the present invention;</li><li><figref idref="f0016">FIG.16</figref> is a block diagram showing a configuration of a transmission apparatus according to Embodiment 4 of the present invention;</li><li><figref idref="f0017">FIG.17</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of Embodiment 4 of the present invention;</li><li><figref idref="f0018">FIG.18</figref> is a layout of signal points of BPSK modulation on an in-phase I - quadrature Q plane;</li><li><figref idref="f0019">FIG.19</figref> is a layout of signal points of QPSK modulation on an in-phase I - quadrature Q plane;</li><li><figref idref="f0020">FIG.20</figref> is a block diagram showing a configuration of a reception apparatus according to Embodiment 4 of the present invention;</li><li><figref idref="f0021">FIG.21</figref> is a block diagram showing a configuration of a transmission apparatus according to Embodiment 5 of the present invention;</li><li><figref idref="f0022">FIG.22</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of the Embodiment 5 of the present invention;</li><li><figref idref="f0023">FIG.23</figref> is a layout of signal points of 16QAM, a known pilot symbol and symbols before and after the pilot symbol on an in-phase I - quadrature Q plane;</li><li><figref idref="f0024">FIG.24</figref> is a layout of signal points of 8PSK modulation, a known pilot symbol and symbols before and after the pilot symbol on an in-phase I - quadrature Q plane; and</li><li><figref idref="f0025">FIG.25</figref> is a block diagram showing a configuration of a reception apparatus according to Embodiment 5 of the present invention.</li></ul>

DETAILED DESCRIPTION OF

THE PREFERRED EMBODIMENT

0009With reference now to the attached drawings, embodiments of the present invention will be explained in detail below.

(Embodiment 1)

0010Embodiment 1 describes a digital radio communication method by which the interval of inserting a known pilot symbol and the modulation system of information symbols are changed according to the communication situation.

0011<figref idref="f0001">FIG.1</figref> is a block diagram showing a configuration of a transmission apparatus according to this embodiment. As shown in <figref idref="f0001">FIG.1</figref>, the transmission apparatus according to this embodiment mainly consists of frame configuration determination section 101, quadrature baseband modulation section 102, pilot symbol generation section 103, frame configuration section 104, and LPFs(Low Pass Filters)105 and 106, transmission radio section 107 and transmission antenna 108.

0012Frame configuration determination section 101 judges the communication situation based on transmission path information which shows the degree of fluctuations of the transmission path due to fading and data transmission speed information which shows the transmission speed of transmission data based on the level of a reception signal and decides the interval of inserting a known pilot symbol and the modulation system of a transmission digital signal. Then, frame configuration determination section 101 outputs a signal indicating the determined modulation system to quadrature baseband modulation section 102 and outputs a signal indicating the determined interval of inserting the known pilot symbol to frame configuration section 104. By the way, details of the method of determining a frame configuration by frame configuration determination section 101 will be described later.

0013Here, when an identical frequency band is used for the uplink and the downlink, the situation of fluctuations in the transmission path due to fading can be estimated from a transition in the result of measuring the reception level of the modulated signal transmitted from the other end of communication on the receiving side, which is not shown in the figure, of the communication apparatus in which the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> is mounted. Furthermore, the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> can recognize the situation of fluctuations in the transmission path due to fading, by the reception apparatus, which is the other end of communication of the transmission apparatus shown in <figref idref="f0001">FIG.1</figref>, measuring the reception level of the modulated signal transmitted from the other end of communication, estimating the situation of fluctuations in the transmission path due to fading based on the transition of the measurement result.

0014Then, when an identical frequency band is used for the uplink and the downlink, the transmission speed of the transmission data can be determined from a result of measuring the reception level of the modulated signal transmitted from the other end of communication on the receiving side, which is not shown in the figure, of the communication apparatus in which the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> is mounted. Furthermore, the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> can recognize the transmission speed of the transmission data by the reception apparatus, which is the other end of communication of the transmission apparatus shown in <figref idref="f0001">FIG.1</figref>, measuring the reception level of the pilot symbol transmitted from the other end of communication and determining the transmission speed of the transmission data based on the measurement result.

0015Quadrature baseband modulation section 102 modulates a transmission digital signal to a quadrature baseband signal with the modulation system indicated from frame configuration determination section 101 and outputs the in-phase component and the quadrature component of the quadrature baseband signal to frame configuration section 104.

0016Pilot symbol generation section 103 generates a pilot symbol known between the transmitting and receiving sides and outputs the in-phase component and the quadrature component of the known pilot symbol to frame configuration section 104.

0017Frame configuration section 104 inserts the known pilot symbol output from pilot symbol generation section 103 into the output signal of quadrature baseband modulation section 102 at the insertion interval instructed from frame configuration determination section 101 and composes a frame.

0018LPF 105 lets pass only a predetermined frequency band section of the in-phase component output from frame configuration section 104. LPF 106 lets pass only a predetermined frequency band section of the quadrature component output from frame configuration section 104.

0019Transmission radio section 107 transmits a radio frequency signal as the electric wave from transmission antenna 108 after performing radio processing on the output signals of LPF 105 and LPF 106.

0020Next, examples of the method of determining a frame configuration by frame configuration determination section 101 of the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> above will be explained.

0021<figref idref="f0002">FIG.2</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of this embodiment and shows a time-symbol relationship. (201) is a frame configuration when the modulation system of information symbols is 16-value quadrature amplitude modulation (16QAM: 16 Quadrature Amplitude Modulation) and a known pilot symbol interval is N symbols. (202) is a frame configuration when the modulation system of information symbols is 16QAM and a known pilot symbol interval is M symbols. (203) is a frame configuration when the modulation system of information symbols is 8 phases (8PSK: 8 Phase Shift Keying) modulation and a known pilot symbol interval is N symbols. (204) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a known pilot symbol interval is M symbols. Suppose N&lt;M at this time.

0022Frame configuration determination section 101 selects one of (201), (202), (203) or (204) in <figref idref="f0002">FIG.2</figref> as the optimal frame configuration based on the transmission path information and the request data transmission speed information.

0023For example, in the case of high-speed fading, frame configuration determination section 101 sacrifices data transmission efficiency on the receiving side and selects a frame configuration of either (201) or (203) in <figref idref="f0002">FIG.2</figref> so that the interval of inserting a known pilot symbol becomes narrower to prevent deterioration of the data demodulation error rate and maintain the quality of data. On the other hand, in the case of low-speed fading, frame configuration determination section 101 selects a frame configuration of either (202) or (204) in <figref idref="f0002">FIG.2</figref> to widen the interval of inserting a known pilot symbol to improve the data transmission efficiency.

0024Also, when the level of the reception signal is large, frame configuration determination section 101 gives priority to data transmission efficiency on the receiving side and selects a frame configuration of either (201) or (202) in <figref idref="f0002">FIG. 2</figref> adopting 16QAM as the modulation system of information symbols. On the other hand, when the level of the reception signal is small, frame configuration determination section 101 gives priority to increasing error resistance while sacrificing data transmission efficiency on the receiving side and selects a frame configuration of either (203) or (204) in <figref idref="f0002">FIG.2</figref> adopting 8PSK as the modulation system of information symbols.

0025<figref idref="f0003">FIG.3</figref> shows a signal point layout according to the 16QAM modulation system on the in-phase I - quadrature Q plane and signal point layout of a known pilot symbol. Signal point 301 is the signal point of a known pilot symbol and signal points 302 are the signal points of 16QAM modulation symbols. <figref idref="f0004">FIG.4</figref> shows a signal point layout according to the 8PSK modulation system on the in-phase I - quadrature Q plane and signal point layout of a known pilot symbol. Signal point 401 is the signal point of a known pilot symbol and signal points 402 are the signal points of 8PSK modulation symbols.

0026<figref idref="f0005">FIG.5</figref> is a block diagram showing a configuration of the reception apparatus according to this embodiment. As shown in <figref idref="f0005">FIG.5</figref>, the reception apparatus according to this Embodiment mainly consists of reception antenna 501, reception radio section 502, transmission path distortion estimation section 503 and detection section 504.

0027Reception radio section 502 receives the radio signal received by reception antenna 501 as an input, performs predetermined radio processing and outputs the in-phase component and the quadrature component of the reception quadrature baseband signal.

0028Transmission path distortion estimation section 503 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, extracts the signal of the known pilot symbol shown in <figref idref="f0003">FIG.3</figref> and <figref idref="f0004">FIG.4</figref> above, estimates the amount of transmission path distortion from the reception condition of the known pilot symbol and outputs the amount of transmission path distortion to detection section 504.

0029Detection section 504 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, detects information symbols based on the amount of transmission path distortion and outputs a reception digital signal.

0030Thus, changing the interval of inserting a known pilot symbol and the modulation system of information symbols according to the communication situation such as fluctuations in the transmission path and the level of the reception signal can improve both the data transmission efficiency and the quality of data at the same time.

0031Here, this embodiment explains two kinds of the interval of inserting a known pilot symbol, but the present invention is not limited to this. Furthermore, this embodiment explains two kinds of the modulation system of information symbols, 16QAM and the 8PSK modulation, but the present invention is not limited to this.

0032Furthermore, this embodiment only explains the frame configuration of information symbols and a known pilot symbol shown in <figref idref="f0002">FIG.2</figref>, but since it is also possible to consider a frame configuration in which signals such as a symbol for synchronization to adjust timing between the receiver and transmitter and a symbol to correct an error on the receiver side are inserted, the present invention is not limited to the frame configuration composed of only information symbols and known pilot symbol.

(Embodiment 2)

0033Embodiment 2 describes a digital radio communication method by which the interval of inserting a BPSK modulation symbol and the modulation system of information symbols other than the above BPSK modulation symbol are changed according to the communication situation.

0034<figref idref="f0006">FIG. 6</figref> is a block diagram showing a configuration of the transmission apparatus according to this Embodiment. Here, in the transmission apparatus shown in <figref idref="f0006">FIG. 6</figref>, the components common to those in the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> are assigned the same reference numerals as those in <figref idref="f0001">FIG.1</figref> and their explanations will be omitted.

0035In the transmission apparatus in <figref idref="f0006">FIG.6</figref>, frame configuration determination section 601 differs in the way of operation from the frame configuration determination section 101 in <figref idref="f0001">FIG.1</figref>. Also, when compared to <figref idref="f0001">FIG.1</figref>, the transmission apparatus in <figref idref="f0006">FIG.6</figref> adopts the configuration with BPSK symbol modulation section 602, instead of pilot symbol generation section 103, added.

0036Frame configuration determination section 601 judges the communication situation, determines the interval of inserting a BPSK modulation symbol and the modulation system of a transmission digital signal, outputs a signal indicating the determined modulation system to quadrature baseband modulation section 102 and outputs a signal indicating the interval of inserting the determined BPSK modulation symbol to quadrature baseband modulation section 102, BPSK symbol modulation section 602 and frame configuration section 104.

0037BPSK symbol modulation section 602 performs BPSK-modulation on the transmission digital signal at the timing indicated from frame configuration determination section 601 and outputs the in-phase component and the quadrature component of the BPSK modulation symbol to frame configuration section 104.

0038<figref idref="f0007">FIG. 7</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of this embodiment and shows a time-symbol relationship. (701) is a frame configuration when the modulation system of information symbols is 16QAM and a BPSK modulation symbol interval is N symbols. (702) is a frame configuration when the modulation system of information symbols is 16QAM and a BPSK modulation symbol interval is M symbols. (703) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a BPSK modulation symbol interval is N symbols. (704) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a BPSK modulation symbol interval is M symbols. Suppose N&lt;M at this time.

0039Frame configuration determination section 601 selects one of (701), (702), (703) or (704) in <figref idref="f0007">FIG.7</figref> as the optimal frame configuration based on the transmission path information and the request data transmission speed information.

0040For example, in the case of high-speed fading, frame configuration determination section 601 sacrifices data transmission efficiency on the receiving side and selects a frame configuration of either (701) or (703) in <figref idref="f0007">FIG.7</figref> so that the interval of inserting a BPSK modulation symbol becomes narrower to prevent deterioration of the data demodulation error rate and maintain the quality of data. On the other hand, in the case of low-speed fading, frame configuration determination section 601 selects a frame configuration of either (702) or (704) in <figref idref="f0007">FIG. 7</figref> to widen the interval of inserting a BPSK modulation symbol to improve the data transmission efficiency.

0041Furthermore, when the level of the reception signal is large, frame configuration determination section 601 gives priority to data transmission efficiency on the receiving side and selects a frame configuration of either (701) or (702) in the <figref idref="f0007">FIG. 7</figref> adopting 16QAM as the modulation system of information symbols. On the other hand, when the level of the reception signal is small, frame configuration determination section 601 gives priority to increasing error resistance while sacrificing data transmission efficiency on the receiving side and selects a frame configuration of either (703) or (704) in <figref idref="f0007">FIG. 7</figref> adopting 8PSK as the modulation system of information symbols.

0042<figref idref="f0008">FIG.8</figref> shows a signal point layout according to the 16QAM modulation system on the in-phase I - quadrature Q plane and signal point layout of BPSK modulation symbols. Signal points 801 are the signal points of BPSK modulation symbols and signal points 802 are the signal points of 16QAM modulation symbols. <figref idref="f0009">FIG.9</figref> shows a signal point layout according to the 8PSK modulation system on the in-phase I - quadrature Q plane and signal point layout of BPSK modulation symbols. Signal points 901 are the signal points of BPSK modulation symbols and signal points 902 are the signal points of 8PSK modulation symbols.

0043<figref idref="f0010">FIG. 10</figref> is a block diagram showing a configuration of the reception apparatus according to this Embodiment. In the reception apparatus shown in <figref idref="f0010">FIG. 10</figref>, the components common to the reception apparatus shown in <figref idref="f0005">FIG.5</figref> are assigned the same reference numerals as those in <figref idref="f0005">FIG. 5</figref> and their explanations will be omitted.

0044In the reception apparatus in <figref idref="f0010">FIG.10</figref>, transmission path distortion estimation section 1001 differs in the way of operation from transmission path distortion estimation section 503 in <figref idref="f0005">FIG.5</figref> and detection section 1002 differs in the way of operation from detection section 504 in <figref idref="f0005">FIG.5</figref>.

0045Transmission path distortion estimation section 1001 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, extracts the signals of the BPSK modulation symbols shown in <figref idref="f0008">FIG.8</figref> and <figref idref="f0009">FIG.9</figref> above, estimates the amount of transmission path distortion from the reception condition of the BPSK modulation symbols and outputs the amount of transmission path distortion to detection section 1002.

0046Detection section 1002 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, detects information symbols and BPSK modulation symbols based on the amount of transmission path distortion and outputs a reception digital signal.

0047Thus, in this embodiment, by sending information with BPSK modulation symbols, instead of a known pilot symbol, inserted, it is possible to improve the transmission speed compared with Embodiment 1.

0048Here, this embodiment describes two kinds of the interval of inserting BPSK modulation symbols but the present invention is not limited to this. Also, this embodiment describes two kinds of the modulation system of information symbols, 16QAM and 8PSK modulation, but the present invention is not limited to this.

0049Furthermore, this embodiment describes the frame configuration of only information symbols and BPSK modulation symbols shown in <figref idref="f0007">FIG.7</figref> but the present invention is not limited to this frame configuration.

(Embodiment 3)

0050Embodiment 3 describes a digital radio communication method by which the interval of inserting QPSK modulation symbols and the modulation system of information symbols other than the above QPSK modulation symbols are changed according to the communication situation.

0051<figref idref="f0011">FIG. 11</figref> is a block diagram showing a configuration of the transmission apparatus according to this Embodiment. In the transmission apparatus shown in <figref idref="f0011">FIG.11</figref>, the components common to those in the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> are assigned the same reference numerals as those in <figref idref="f0001">FIG.1</figref> and their explanations will be omitted.

0052In the transmission apparatus in <figref idref="f0011">FIG.11</figref>, frame configuration determination section 1101 differs in the way of operation from the frame configuration determination section 101 in <figref idref="f0001">FIG.1</figref>. Also, when compared to <figref idref="f0001">FIG.1</figref>, the transmission apparatus in <figref idref="f0011">FIG.11</figref> adopts a configuration with QPSK symbol modulation section 1102, instead of pilot symbol generation section 103, added.

0053Frame configuration determination section 1101 judges the communication situation, determines the interval of inserting QPSK modulation symbols and the modulation system of a transmission digital signal, outputs a signal indicating the determined modulation system to quadrature baseband modulation section 102 and outputs a signal indicating the determined interval of inserting QPSK modulation symbols to quadrature baseband modulation section 102, QPSK symbol modulation section 1102 and frame configuration section 104.

0054QPSK symbol modulation section 1102 performs QPSK-modulation on a transmission digital signal at the timing indicated from frame configuration determination section 1101 and outputs the in-phase component and the quadrature component of the QPSK modulation symbol to frame configuration section 104.

0055<figref idref="f0012">FIG.12</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of this embodiment and shows a time-symbol relationship. (1201) is a frame configuration when the modulation system of information symbols is 16QAM and a QPSK modulation symbol interval is N symbols. (1202) is a frame configuration when the modulation system of information symbols is 16QAM and a QPSK modulation symbol interval is M symbols. (1203) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a QPSK modulation symbol interval is N symbols. (1204) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a QPSK modulation symbol interval is M symbols. Suppose N&lt;M at this time.

0056Frame configuration determination section 1101 selects one of (1201), (1202), (1203) or (1204) in <figref idref="f0012">FIG.12</figref> as the optimal frame configuration based on the transmission path information and the request data transmission speed information.

0057For example, in the case of high-speed fading, frame configuration determination section 1101 sacrifices data transmission efficiency on the receiving side and selects a frame configuration of either (1201) or (1203) in <figref idref="f0012">FIG.12</figref> so that the QPSK modulation symbol insertion interval becomes narrower to prevent deterioration of the data demodulation error rate and maintain the quality of data. On the other hand, in the case of low-speed fading, frame configuration determination section 1101 selects a frame configuration of either (1202) or (1204) in <figref idref="f0012">FIG.12</figref> to widen the interval of inserting QPSK modulation symbols to improve the data transmission efficiency.

0058Furthermore, when the level of the reception signal is large, frame configuration determination section 1101 gives priority to data transmission efficiency on the receiving side and selects a frame configuration of either (1201) or (1202) in <figref idref="f0012">FIG.12</figref> adopting 16QAM as the modulation system of information symbols. On the other hand, when the level of the reception signal is small, frame configuration determination section 1101 gives priority to increasing error resistance while sacrificing data transmission efficiency on the receiving side and selects a frame configuration of either (1203) or (1204) in <figref idref="f0012">FIG.12</figref> adopting 8PSK as the modulation system of information symbols.

0059<figref idref="f0013">FIG.13</figref> shows a signal point layout according to the 16QAM modulation system on the in-phase I - quadrature Q plane and signal point layout of QPSK modulation symbols. Signal points 1301 are the signal points of QPSK modulation symbols and signal points 1302 are the signal points of 16QAM modulation symbols. <figref idref="f0014">FIG.14</figref> shows a signal point layout according to the 8PSK modulation system on the in-phase I - quadrature Q plane and signal point layout of QPSK modulation symbols. Signal points 1401 are the signal points of QPSK modulation symbols and signal points 1402 are the signal points of 8PSK modulation symbols.

0060<figref idref="f0015">FIG.15</figref> is a block diagram showing a configuration of the reception apparatus according to this embodiment. In the reception apparatus shown in <figref idref="f0015">FIG.15</figref>, the components common to the reception apparatus shown in <figref idref="f0005">FIG.5</figref> are assigned the same reference numerals as those in <figref idref="f0005">FIG. 5</figref> and their explanations will be omitted.

0061In the reception apparatus in <figref idref="f0015">FIG.15</figref>, transmission path distortion estimation section 1501 differs in the way of operation from transmission path distortion estimation section 503 in <figref idref="f0005">FIG.5</figref> and detection section 1502 differs in the way of operation from detection section 504 in <figref idref="f0005">FIG.5</figref>.

0062Transmission path distortion estimation section 1501 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, extracts the signals of the QPSK modulation symbols shown in <figref idref="f0013">FIG.13</figref> and <figref idref="f0014">FIG.14</figref> above, estimates the amount of transmission path distortion from the reception condition of the QPSK modulation symbols and outputs the amount of transmission path distortion to detection section 1502.

0063Detection section 1502 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, detects information symbols and QPSK modulation symbols based on the amount of transmission path distortion and outputs a reception digital signal.

0064Thus, in this embodiment, by sending information with QPSK modulation symbols, instead of a known pilot symbol, inserted, it is possible to improve the transmission speed compared with Embodiment 1 and Embodiment 2.

0065Here, this embodiment describes two kinds of the interval of inserting QPSK modulation symbols but the present invention is not limited to this. Also, this embodiment describes two kinds of the modulation system of information symbols, 16QAM and 8PSK modulation, but the present invention is not limited to this.

0066Furthermore, this embodiment describes the frame configuration of only information symbols and QPSK modulation symbols shown in <figref idref="f0012">FIG. 12</figref> but the present invention is not limited to this frame configuration.

(Embodiment 4)

0067Embodiment 4 describes a digital radio communication method by which the modulation system of information symbols is changed according to the communication situation and when the modulation system of information symbols uses 8 or more values, a known pilot symbol is inserted with the insertion interval changed according to the communication situation.

0068<figref idref="f0016">FIG.16</figref> is a block diagram showing a configuration of the transmission apparatus according to this Embodiment. In the transmission apparatus shown in <figref idref="f0016">FIG.16</figref>, the components common to those in the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> are assigned the same reference numerals as those in <figref idref="f0001">FIG.1</figref> and their explanations will be omitted.

0069In the transmission apparatus in <figref idref="f0016">FIG.16</figref>, frame configuration determination section 1601 differs in the way of operation from the frame configuration determination section 101 in <figref idref="f0001">FIG.1</figref>.

0070Frame configuration determination section 1601 determines the modulation system of a transmission digital signal based on the communication situation and outputs a signal indicating the determined modulation system to quadrature baseband modulation section 102. Also, when the determined modulation system uses 8 or more values, frame configuration determination section 1601 determines the interval of inserting a pilot symbol based on the communication situation and outputs a signal indicating the determined interval of inserting the pilot symbol to frame configuration section 104. Also, when the determined modulation system uses 8 fewer values, frame configuration determination section 1601 outputs a signal giving an instruction for stopping the generation of pilot symbols to pilot symbol generation section 103.

0071Pilot symbol generation section 103 generates a pilot symbol known between the transmitting and receiving sides and outputs the in-phase component and the quadrature component of the known pilot symbol to frame configuration section 104. However, when instructed to stop the generation of pilot symbols from frame configuration determination section 1601, pilot symbol generation section 103 stops operation.

0072<figref idref="f0017">FIG.17</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of this embodiment and shows a time-symbol relationship. (1701) is a frame configuration when the modulation system of information symbols is BPSK. (1702) is a frame configuration when the modulation system of information symbols is QPSK.

0073The ranking of the frame configurations shown in <figref idref="f0002">FIG. 2</figref> and <figref idref="f0017">FIG.17</figref> in descending order of resistance to fading speed is (1701), (1702), (203), (201), (204) and (202). Furthermore, the ranking in descending order of error resistance is (1701), (1702), (203), (204), (201) and (202). On the other hand, the ranking in descending order of data transmission efficiency on the receiving side is (202), (201), (204), (203), (1702) and (1701).

0074Frame configuration determination section 1601 selects one of (201), (202), (203) or (204) in <figref idref="f0002">FIG.2</figref> or (1701) or (1702) in <figref idref="f0017">FIG.17</figref> above as the optimal frame configuration based on the transmission path information and the request data transmission speed information.

0075<figref idref="f0018">FIG.18</figref> shows a signal point layout according to the BPSK modulation method on the in-phase I - quadrature Q plane and signal points 1801 are the signal points of BPSK symbols.

0076<figref idref="f0019">FIG.19</figref> shows a signal point layout according to the QPSK modulation method on the in-phase I - quadrature Q plane and signal points 1901 are the signal points of QPSK symbols.

0077<figref idref="f0020">FIG. 20</figref> is a block diagram showing a configuration of the reception apparatus according to this embodiment. In the reception apparatus shown in <figref idref="f0020">FIG.20</figref>, the components common to those in the reception apparatus shown in <figref idref="f0005">FIG.5</figref> are assigned the same reference numerals as those in <figref idref="f0005">FIG.5</figref> and their explanations will be omitted.

0078In the reception apparatus in <figref idref="f0020">FIG.20</figref>, transmission path distortion estimation section 2001 differs in the way of operation from transmission path estimation section 503 in <figref idref="f0005">FIG.5</figref> and detection section 2002 differs in the way of operation from detection section 504 in <figref idref="f0005">FIG.5</figref>.

0079Transmission path distortion estimation section 2001 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, estimates the amount of transmission path distortion from the reception condition of the BPSK modulation symbol shown in <figref idref="f0018">FIG.18</figref> or the QPSK modulation symbol shown in <figref idref="f0019">FIG.19</figref> and outputs the amount of transmission path distortion to detection section 2002.

0080Detection section 2002 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, detects information symbols based on the amount of transmission path distortion and outputs a reception digital signal.

0081In this way, by changing the modulation system of information symbols according to the communication situation such as fluctuations in the transmission path and the level of the reception signal, inserting a known pilot symbol when the information symbol modulation system is a multi-value modulation system with 8 or more values and changing the interval of inserting the above known pilot symbol according to the communication situation, it is possible to improve both the data transmission efficiency and the quality of data at the same time.

0082Here, in this embodiment, the transmission apparatus in <figref idref="f0016">FIG.16</figref> can also have a configuration equipped with BPSK symbol modulation section 602 shown in <figref idref="f0006">FIG.6</figref> instead of pilot symbol generation section 103.

0083In this case, frame configuration determination section 1601 determines the modulation system of the transmission digital signal based on the communication situation. For example, frame configuration determination section 1601 selects one of (701), (702), (703) or (704) in <figref idref="f0007">FIG.7</figref> above or (1701) or (1702) in <figref idref="f0017">FIG.17</figref> as the optimal frame configuration.

0084Then, frame configuration determination section 1601 outputs the signals indicating the determined modulation system to quadrature baseband modulation section 102. Also, when the determined modulation system uses 8 or more values, frame configuration determination section 1601 determines the interval of inserting BPSK modulation symbols based on the communication situation and outputs a signal indicating the determined interval of inserting the BPSK modulation symbols to BPSK symbol modulation section 602 and frame configuration section 104. Furthermore, when the determined modulation system is 8 fewer values, frame configuration determination section 1601 outputs a signal giving an instruction for stopping the generation of BPSK modulation symbols to BPSK symbol modulation section 602.

0085BPSK symbol modulation section 602 performs BPSK-modulation on a transmission digital signal at the timing indicated from frame configuration determination section 1601 and outputs the in-phase component and the quadrature component of the BPSK modulation symbols to frame configuration section 104. However, when instructed to stop the generation of BPSK modulation symbols from frame configuration determination section 1601, BPSK symbol modulation section 602 stops operation.

0086Transmission path distortion estimation section 2001 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, estimates the amount of transmission path distortion from the reception condition of the BPSK modulation symbols shown in <figref idref="f0008">FIG.8</figref> and <figref idref="f0009">FIG.9</figref> above, the BPSK modulation symbols shown in <figref idref="f0018">FIG.18</figref> or the QPSK modulation symbols shown in <figref idref="f0019">FIG.19</figref> and outputs the amount of transmission path distortion to detection section 2002.

0087Furthermore, in this embodiment, the transmission apparatus in <figref idref="f0016">FIG.16</figref> .can also have a configuration equipped with QPSK symbol modulation section 1102 shown in <figref idref="f0011">FIG.11</figref> instead of pilot symbol generation section 103.

0088In this case, frame configuration determination section 1601 determines the modulation system of the transmission digital signal based on the communication situation. For example, frame configuration determination section 1601 selects one of (1201), (1202), (1203) or (1204) in <figref idref="f0012">FIG.12</figref> above or (1701) or (1702) in <figref idref="f0017">FIG.17</figref> as the optimal frame configuration.

0089Then, frame configuration determination section 1601 outputs a signal indicating the determined modulation system to quadrature baseband modulation section 102. Also, when the determined modulation system uses 8 or more values, frame configuration determination section 1601 determines the interval of inserting QPSK modulation symbols based on the communication situation and outputs a signal indicating the determined interval of inserting the QPSK symbols to QPSK symbol modulation section 1102 and frame configuration section 104. Also, when the determined modulation system is 8 fewer values, frame configuration determination section 1601 outputs a signal giving an instruction for stopping the generation of QPSK modulation symbols to QPSK symbol modulation section 1102.

0090QPSK symbol modulation section 1102 performs QPSK-modulation on a transmission digital signal at the timing indicated from frame configuration determination section 1601 and outputs the in-phase component and the quadrature component of the QPSK modulation symbols to frame configuration section 104. However, when instructed to stop generating QPSK modulation symbols from frame configuration determination section 1601, QPSK symbol modulation section 1102 stops operation.

0091Transmission path distortion estimation section 2001 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, estimates the amount of transmission path distortion from the reception condition of the QPSK modulation symbols shown in <figref idref="f0013">FIG.13</figref> or <figref idref="f0014">FIG.14</figref> and the BPSK modulation symbols shown in <figref idref="f0018">FIG.18</figref> or the QPSK modulation symbol shown in <figref idref="f0019">FIG.19</figref> and outputs the amount of transmission path distortion to detection section 2002.

0092Here, this embodiment explains two kinds of the interval of inserting a known pilot symbol, but the present invention is not limited to this. Also, this embodiment explains two kinds of the multi-value modulation system with 8 or more values of information symbols, 16QAM and the 8PSK modulation, but the present invention is not limited to this.

0093Furthermore, this embodiment describes the frame configurations in <figref idref="f0002">FIG. 2</figref>, <figref idref="f0007">FIG. 7</figref>, <figref idref="f0012">FIG. 12</figref> and <figref idref="f0017">FIG. 17</figref> but the present invention is not limited to these frame configurations.

0094Furthermore, the BPSK modulation method and the QPSK modulation method of the modulation system of information symbols of the present invention are not limited to the signal point layouts shown in <figref idref="f0018">FIG.18</figref> and <figref idref="f0019">FIG.19</figref> but π/2 shift BPSK modulation or π/4 shift QPSK modulation can also be used.

(Embodiment 5)

0095Embodiment 5 describes a digital radio communication method by which the interval of inserting a known pilot symbol, the number of signal points with one symbol immediately before and after a known pilot symbol (hereinafter referred to as "symbols before and after a pilot") and signal point layout and the modulation system of information symbols other than those symbols are changed.

0096<figref idref="f0021">FIG.21</figref> is a block diagram showing a configuration of the transmission apparatus according to this embodiment. In the transmission apparatus shown in <figref idref="f0021">FIG.21</figref>, the components common to those in the transmission apparatus shown in <figref idref="f0001">FIG.1</figref> are assigned the same reference numerals as those shown in <figref idref="f0001">FIG.1</figref> and their explanations will be omitted.

0097In the transmission apparatus in <figref idref="f0021">FIG.21</figref>, frame configuration determination section 2101 differs in the way of operation from frame configuration determination section 101 in <figref idref="f0001">FIG.1</figref>. Furthermore, the transmission apparatus in <figref idref="f0021">FIG.21</figref> adopts a configuration with symbols before and after a pilot modulation section 2102 added compared to <figref idref="f0001">FIG.1</figref>.

0098Frame configuration determination section 2101 determines the interval of inserting a known pilot symbol and the modulation system of a transmission digital signal based on the communication situation. In this case, frame configuration determination section 2101 uses different modulation systems for symbols before and after a pilot and for other information symbols.

0099Then, frame configuration determination section 2101 outputs a signal indicating the modulation system of symbols before and after a pilot to symbols before and after a pilot modulation section 2102, outputs a signal indicating the modulation system of other information symbols to quadrature baseband modulation section 102 and outputs a signal indicating the interval of inserting the determined known pilot symbol to symbols before and after a pilot modulation section 2102 and frame configuration section 104.

0100Symbols before and after a pilot modulation section 2102 modulates on a transmission digital signal by predetermined modulation system at the timing indicated from frame configuration determination section 2101 and outputs the in-phase component and the quadrature component of the symbols before and after a pilot to frame configuration section 104.

0101<figref idref="f0022">FIG.22</figref> illustrates examples of a frame configuration of a signal transmitted from the transmission apparatus of this embodiment and shows a time-symbol relationship. (2201) is a frame configuration when the modulation system of information symbols is 16QAM and a known pilot symbol interval is N symbols. (2202) is a frame configuration when the modulation system of information symbols is 16QAM and a known pilot symbol interval is M symbols. (2203) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a known pilot symbol interval is N symbols. (2204) is a frame configuration when the modulation system of information symbols is 8PSK modulation and a known pilot symbol interval is M symbols. Suppose N&lt;M at this time.

0102Signal point 2211 is 1 symbol immediately before the known pilot symbol when the information symbol modulation system is 16QAM and signal point 2212 is 1 symbol immediately after the known pilot symbol when the information symbol modulation system is 16QAM. Signal point 2213 is 1 symbol immediately before the known pilot symbol when the information symbol modulation system is 8PSK modulation and signal point 2214 is 1 symbol immediately after the known pilot symbol when the information symbol modulation system is 8PSK modulation.

0103Frame configuration determination section 2101 selects one of (2201), (2202), (2203) or (2204) in <figref idref="f0022">FIG.22</figref> as the optimal frame configuration based on the transmission path information and the request data transmission speed information.

0104For example, in the case of high-speed fading, frame configuration determination section 2101 sacrifices data transmission efficiency on the receiving side and selects a frame configuration of either (2201) or (2203) in <figref idref="f0022">FIG.22</figref> so that the interval of inserting a known pilot symbol becomes narrower to prevent deterioration of the data demodulation error rate and maintain the quality of data. On the other hand, in the case of low-speed fading, frame configuration determination section 2101 selects a frame configuration of either (2202) or (2204) in <figref idref="f0022">FIG. 22</figref> to widen the interval of inserting a known pilot symbol to improve the data transmission efficiency.

0105Furthermore, when the level of the reception signal is large, frame configuration determination section 2101 gives priority to data transmission efficiency on the receiving side and selects a frame configuration of either (2201) or (2202) in <figref idref="f0022">FIG. 22</figref> adopting 16QAM as the modulation system of information symbols. On the other hand, when the level of the reception signal is small, frame configuration determination section 2101 gives priority to increasing error resistance while sacrificing data transmission efficiency on the receiving side and selects a frame configuration of either (2203) or (2204) in <figref idref="f0022">FIG.22</figref> adopting 8PSK as the modulation system of information symbols.

0106<figref idref="f0023">FIG. 23</figref> shows a signal point layout according to the 16QAM modulation method on the in-phase I - quadrature Q plane and a signal point layout according to a known pilot symbol and a signal point layout of symbols before and after a pilot. Signal point 2301 is the signal point of a known pilot symbol, signal points 2302 are the signal points of 16QAM modulation symbols and signal points 2303 are the signal points of symbols before and after a pilot.

0107<figref idref="f0024">FIG.24</figref> shows a signal point layout according to the 8PSK modulation system on the in-phase I - quadrature Q plane, a signal point layout of a known pilot symbol and a signal point layout of symbols before and after a pilot. Signal points 2401, 2401-A and 2401-B are the signal points of 8PSK modulation symbols, 2401-A is the signal point of the known pilot symbol, 2401-A and 2401-B are the signal points of symbols before and after a pilot and straight line 2402 is the straight line formed by linking the signal point of the known pilot symbol and the origin on the in-phase I - quadrature Q plane.

0108<figref idref="f0025">FIG. 25</figref> is a block diagram showing a configuration of the reception apparatus according to this embodiment. In the reception apparatus shown in <figref idref="f0025">FIG.25</figref>, the components common to those in the reception apparatus shown in <figref idref="f0005">FIG.5</figref> are assigned the same reference numerals as those shown in <figref idref="f0005">FIG.5</figref> and their explanations will be omitted.

0109In the reception apparatus in <figref idref="f0025">FIG.25</figref>, transmission path estimation section 2501 differs in the way of operation from transmission path estimation section 503 and detection section 2502 differs in the way of operation from detection section 504 in <figref idref="f0005">FIG.5</figref>.

0110Transmission path distortion estimation section 2501 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, extracts the signal of the known pilot symbol shown in <figref idref="f0023">FIG.23</figref> and <figref idref="f0024">FIG.24</figref> above, estimates the amount of transmission path distortion from the reception condition of the known pilot symbol and outputs the amount of transmission path distortion to detection section 2502.

0111Detection section 2502 receives the in-phase component and the quadrature component of the quadrature baseband signal as inputs, detects information symbols including symbols before and after a pilot based on the amount of transmission path distortion and outputs a reception digital signal.

0112Thus, changing the interval of inserting a known pilot symbol and the modulation system of information symbols according to the communication situation such as fluctuations in the transmission path and the level of the reception signal can improve both the data transmission efficiency and the quality of data at the same time.

0113Furthermore, as shown in <figref idref="f0023">FIG. 23</figref> and <figref idref="f0024">FIG. 24</figref>, by arranging two or more signal points before and after a pilot on the straight line formed by linking the origin and the signal point of the known pilot symbol on the in-phase I - quadrature Q plane, it is possible for the reception apparatus in <figref idref="f0025">FIG.25</figref> to suppress deterioration of the estimation accuracy of reference phase and the amount of frequency offset by the pilot symbol, even if symbol synchronization is not established completely when a reference phase and the amount of frequency offset is estimated from the pilot signal. When detection section 116 performs detection, this allows the bit error rate characteristic based on the carrier-to-noise ratio to be improved.

0114Here, this embodiment can be combined with Embodiment 4 above. That is, when the determined modulation system uses 8 or more values, frame configuration determination section 2101 in <figref idref="f0021">FIG.21</figref> determines the interval of inserting a pilot symbol based on the communication situation and outputs a signal indicating the interval of inserting the determined pilot symbol to symbols before and after a pilot modulation section 2102 and frame configuration section 104. Furthermore, when the determined modulation system uses 8 fewer values, frame configuration determination section 2101 outputs a signal giving an instruction for stopping the generation of pilot symbols to symbols before and after a pilot modulation section 2102 and pilot symbol generation section 103.

0115Pilot symbol generation section 103 generates a pilot symbol known between the transmitting and receiving sides and outputs the in-phase component and the quadrature component of the known pilot symbol to frame configuration section 104. However, when instructed to stop the generation of pilot symbols from frame configuration determination section 2101, pilot symbol generation section 103 stops operation.

0116Symbols before and after a pilot modulation section 2102 performs BPSK-modulation or QPSK-modulation on a transmission digital signal at the timing indicated from frame configuration determination section 2101 and outputs the in-phase component and the quadrature component of the symbols before and after a pilot to frame configuration section 104. However, when instructed to stop the generation of pilot symbols from frame configuration determination section 2101, symbols before and after a pilot modulation section 2102 stops operation.

0117This allows the effect of Embodiment 4 to be attained in addition to the effect of this embodiment as described above.

0118Here, this embodiment describes two kinds of modulation system of information symbols, 16QAM and 8PSK modulation, but the present invention is not limited to this.

0119Furthermore, this embodiment explains only the configuration of information symbols, a known pilot symbol, symbols before and after a pilot in <figref idref="f0022">FIG.22</figref>, but the frame configuration of-the present invention is not limited to the frameA configuration composed of only information symbols, a known pilot symbol, symbols before and after a pilot.

0120As described above, according to the present invention, by changing the interval of inserting a known pilot symbol, BPSK modulation symbols or QPSK modulation symbols and the modulation system of information symbols according to the communication situation of fluctuations in the transmission path and the level of the reception signal, etc., it is possible to improve both the data transmission efficiency and the quality of data at the same time.

0121The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.

0122This application is based on the Japanese Patent Application No.<patcit id="pcit0002" dnum="JPHEI11213289B"><text>HEI 11-213289 filed on July 28, 1999</text></patcit>, entire content of which is expressly incorporated by reference herein.

0123The following is a list of further preferred embodiments of the invention: <ul id="ul0002" list-style="none"><li>Embodiment 1: A transmission apparatus comprising: <ul id="ul0003" list-style="none"><li>1st symbol generating means (102) for modulating a transmission digital signal according to a predetermined modulation system and generating a 1st symbol which is a quadrature baseband signal;</li><li>2nd symbol generating means (103, 602, 1102,) for generating a 2nd symbol;</li><li>frame configuration determining means (101,601,1101,1601,2101) for determining an interval of inserting said 2nd symbol based on the communication situation; and</li><li>frame configuring means (104) for configuring a frame by inserting said 2nd symbol into said 1 st symbol at the insertion interval determined by this frame configuration determining means.</li></ul></li><li>Embodiment 2: The transmission apparatus according to embodiment 1, wherein the frame configuration determining means narrows the interval of inserting the 2nd symbol as a fluctuation in the transmission path increases due to fading.</li><li>Embodiment 3: The transmission apparatus according to embodiment 1, wherein the frame configuration determining means determines the modulation system according to the communication situation and the 1st symbol generating means modulates a transmission digital signal according to the modulation system determined by said frame configuration determining means and generates a 1st symbol.</li><li>Embodiment 4: The transmission apparatus according to embodiment 3, wherein the frame configuration determining means selects a modulation system with more multiple values as the reception level increases.</li><li>Embodiment 5: The transmission apparatus according to embodiment 1, wherein the 2nd symbol generating means (103) generates a pilot symbol known between the transmitting and receiving sides as the 2nd symbol.</li><li>Embodiment 6: The transmission apparatus according to embodiment 5, further comprising: <ul id="ul0004" list-style="none" compact="compact"><li>3rd symbol generating means (2102) for modulating a transmission digital signal according to a predetermined modulation system and generating a 3rd symbol, wherein said 3rd symbol is inserted immediately before and after a pilot symbol.</li></ul></li><li>Embodiment 7: The transmission apparatus according to embodiment 6, wherein the 3rd symbol generating means arranges at least two 3rd symbol signal points on a virtual line linking the origin and pilot symbol signal point in a signal space diagram.</li><li>Embodiment 8: The transmission apparatus according to embodiment 1, wherein the 2nd symbol generating means (602) performs binary phase modulation on a transmission digital signal to generate a 2nd symbol.</li><li>Embodiment 9: The transmission apparatus according to embodiment 1, wherein the 2nd symbol generating means (1102) performs quadrature phase modulation on a transmission digital signal to generate a 2nd symbol.</li><li>Embodiment 10: The transmission apparatus according to embodiment 3, wherein the 2nd symbol generating means switches the 2nd symbol generation method based on the modulation system selected by the frame configuration determining means.</li><li>Embodiment 11: The transmission apparatus according to embodiment 10, wherein, when the frame configuration determining means selects a multi-value modulation system with 8 or more values, the 2nd symbol generating means generates a pilot symbol known between the transmitting and receiving sides as the 2nd symbol.</li><li>Embodiment 12: The transmission apparatus according to embodiment 11, further comprising 3rd symbol generating means for modulating a transmission digital signal according to a predetermined modulation system and creating a 3rd symbol, wherein said 3rd symbol is inserted immediately before and after a pilot symbol.</li><li>Embodiment 13: The transmission apparatus according to embodiment 12, wherein the 3rd symbol generating means arranges at least two 3rd symbol signal points on a virtual line linking the origin and pilot symbol signal point in a signal space diagram.</li><li>Embodiment 14: The transmission apparatus according to embodiment 10, wherein, when the frame configuration determining means selects a multi-value modulation system with 8 or more values, the 2nd symbol generating means performs binary phase modulation on a transmission digital signal to generate a 2nd symbol.</li><li>Embodiment 15: The transmission apparatus according to embodiment 10, wherein, when the frame configuration determining means selects a multi-value modulation system with 8 or more values, the 2nd symbol generating means performs quadrature phase modulation on a transmission digital signal to generate a 2nd symbol.</li><li>Embodiment 16: The transmission apparatus according to embodiment 10, wherein, when the frame configuration determining means selects a modulation system with 8 less values, the 2nd symbol generating means generates no 2nd symbol.</li><li>Embodiment 17: A base station apparatus equipped with a transmission apparatus, said transmission apparatus comprising: <ul id="ul0005" list-style="none"><li>1st symbol generating means for modulating a transmission digital signal according to a predetermined modulation system and generating a 1st symbol which is a quadrature baseband signal;</li><li>2nd symbol generating means for generating a 2nd symbol;</li><li>frame configuration determining means for determining an interval of inserting said 2nd symbol based on the communication situation; and</li><li>frame configuring means for configuring a frame by inserting said 2nd symbol into said 1st symbol at the insertion interval determined by this frame configuration determining means.</li></ul></li><li>Embodiment 18: A communication terminal apparatus equipped with a transmission apparatus, said transmission apparatus comprising: <ul id="ul0006" list-style="none"><li>1st symbol generating means for modulating a transmission digital signal according to a predetermined modulation system and generating a 1 st symbol which is a quadrature baseband signal;</li><li>2nd symbol generating means for generating a 2nd symbol;</li><li>frame configuration determining means for determining an interval of inserting said 2nd symbol based on the communication situation; and</li><li>frame configuring means for configuring a frame by inserting said 2nd symbol into said 1st symbol at the insertion interval determined by this frame configuration determining means.</li></ul></li><li>Embodiment 19: A reception apparatus comprising: <ul id="ul0007" list-style="none"><li>transmission path distortion estimating means for extracting a 2nd symbol from a signal sent from the transmission apparatus according to embodiment 1 and estimating the amount of transmission path distortion from the reception condition of said 2nd symbol; and</li><li>detecting means for detecting information symbols based on said amount of transmission path distortion and outputting a reception digital signal.</li></ul></li><li>Embodiment 20: A base station apparatus equipped with a reception apparatus, said reception apparatus comprising: <ul id="ul0008" list-style="none"><li>transmission path distortion estimating means for extracting a 2nd symbol from a signal sent from the transmission apparatus according to embodiment 1 and estimating the amount of transmission path distortion from the reception condition of said 2nd symbol; and</li><li>detecting means for detecting information symbols based on said amount of transmission path distortion and outputting a reception digital signal.</li></ul></li><li>Embodiment 21: A communication terminal apparatus equipped with a reception apparatus, said reception apparatus comprising: <ul id="ul0009" list-style="none"><li>transmission path distortion estimating means for extracting a 2nd symbol from a signal sent from the transmission apparatus according to embodiment 1 and estimating the amount of transmission path distortion from the reception condition of said 2nd symbol; and</li><li>detecting means for detecting information symbols based on said amount of transmission path distortion and outputting a reception digital signal.</li></ul></li><li>Embodiment 22: A radio communications system that carries out a digital radio communication between the base station apparatus according to embodiment 17 and the communication terminal apparatus according to embodiment 21.</li><li>Embodiment 23: A radio communications system that carries out a digital radio communication between the base station apparatus according to embodiment 20 and the communication terminal apparatus according to embodiment 18.</li><li>Embodiment 24: A digital radio communication method that not only changes the interval of inserting a known pilot symbol according to the communication situation but also changes the modulation system of information symbols other than said known pilot symbol.</li><li>Embodiment 25: A digital radio communication method that changes the interval of inserting binary phase modulation symbols according to the communication situation and changes the modulation system of information symbols other than said binary phase modulation symbols.</li><li>Embodiment 26: A digital radio communication method that changes the interval of inserting quadrature phase modulation symbols according to the communication situation and changes the modulation system of information symbols other than said quadrature phase modulation symbols.</li><li>Embodiment 27: A digital radio communication method that changes the modulation system of information symbols according to the communication situation and when the information symbol modulation system is a multi-value modulation system with 8 or more values, inserts a known pilot symbol and changes the interval of inserting said known pilot symbol according to the communication situation.</li><li>Embodiment 28: A digital radio communication method that changes the modulation system of information symbols according to the communication situation and when the information symbol modulation system is a multi-value modulation system with 8 or more values, inserts binary phase modulation symbols and changes the interval of inserting said binary phase modulation symbols according to the communication situation.</li><li>Embodiment 29: A digital radio communication method that changes the modulation system of Information symbols according to the communication situation and when the information symbol modulation system is a multi-value modulation system with 8 or more values, inserts quadrature phase modulation symbols and changes the interval of inserting said quadrature phase modulation symbols according to the communication situation.</li><li>Embodiment 30: A digital radio communication method that arranges at least two 4th symbols, one immediately before and one immediately after a known pilot symbol on a virtual line linking the origin and known pilot symbol In a signal space diagram and changes the interval of inserting the known pilot symbol, the number of said 4th symbol signal points and signal point layout, and the modulation system of information symbols other than said known pilot symbol and said 4th symbol according to the communication situation.</li><li>Embodiment 31: The digital radio communication method according to embodiment 30 that changes the modulation system of information symbols according to the communication situation and when the modulation system is a multi-value modulation system with 8 or more values, inserts a known pilot symbol and 4th symbol.</li></ul>